1. Field of the Invention
The invention relates to a method of removing polymer in a fabrication process of a semiconductor device, for instance, and further to an apparatus for doing the same.
2. Description of the Related Art
A process of fabricating a semiconductor device, for instance, generally includes a step of forming a metal wire layer at a surface of a semiconductor wafer.
Specifically, a metal wire layer is formed as follows.
First, a metal layer and a barrier layer are formed in this order on a semiconductor wafer. Then, a resist is coated onto the semiconductor wafer, and then, patterned. Then, the metal layer and the barrier layer are dry-etched with the patterned resist being used as a mask. By forming a polymer layer on a sidewall of etched portions in the metal layer while the metal layer is being dry-etched, it is possible to dry-etch the metal layer highly anisotropically and just in accordance with the resist pattern. Then, the resist is removed by dry ashing. Then, the resist residual on the metal layer and polymer layer adhered to a sidewall of the etched metal layer are dissolved by chemicals. Then, the chemicals is rinsed out.
However, the above-mentioned process of removing the polymer layer is accompanied with the problem that, supposing that the metal layer is composed of aluminum (Al), when the chemicals is rinsed out with pure water, the chemicals and pure water react with each other, and resultingly, there is generated solution which corrodes aluminum. For instance, aluminum is most likely to be dissolved in solution containing ammonium fluoride (NH4F) at about 30%.
Even if the chemicals is diluted, since aluminum is readily corroded, aluminum might be dissolved into pure water. In addition, if aluminum contains copper therein, aluminum might be dissolved together with copper as a core due to the cell effect in rinsing the chemicals off with pure water. Furthermore, aluminum thus having been dissolved might be adhered to a semiconductor wafer as contaminants such as metal impurity.
If aluminum of which the metal layer is composed were dissolved, the metal layer would become thin, or would be adhered to a semiconductor wafer as contaminants, resulting in reduction in a yield of fabrication of a semiconductor device.